Feed collet



S. BAXENDALE FEED COLLET April 14; 1936.

Filed Nov. 12, 1934 INVENTOR SAMUEL BAXENDALE ATTORNEYS Patented Apr.14, 1936 UNITED STATES PATENT OFFICE 3 Claims.

The invention relates to feed mechanisms such as used in connection withautomatic machines for the feeding of a bar of. stock, and it is theprimary object of the invention to lessen the waste of material. It is afurther object to obtain a construction which is free from certaindefects in constructions heretofore used, and to this end the inventionconsists in the construction as hereinafter set forth.

In the drawing:

Fig. 1 is a central longitudinal section through the revolving spindleof an automatic machine showing my improved feed collet applied thereto;

Fig. 2 is a similar view of the end portion of the collet showing itengaged with the rear end of a stock bar;

Fig. 3 is a cross section on line 33, Fig. 1;

Fig. 4 is an end elevation of the feed collet;

Fig. 5 is a side elevation-of the feed collet;

Fig. 6 is a similar view showing a slightly modified construction.

In the present state of the art feed collets have been used inconnection with automatic machines these consisting essentially of alongitudinally slotted tubular member having the bars intermediate theslots bowed inward to form resilient gripping jaws for frictionallyengaging the stock bar. With such constructions the collet will beeifective for feeding the stock bar until its rear end passes to theforward end of the bowed bars, after which no further longitudinal feedis possible, inasmuch as the gripping points are necessarily spaced somedistance in rear of the forward end of. the collet. This leaves aportion of the stock bar which can not be used and must be scrapped. Ina modified construction also heretofore used the gripping point isadvanced towards the front end of the collet by giving an abrupt inwardturn to the bars at the forward end and by also slitting one side of thetube through the forward end. The objection to such construction is thatthe abrupt inward bend of the bars concentrates stress at the bend withthe result that collets are frequently broken. Furthermore, even withsuch construction, the stock bar can not be fed to the forward end ofthe feed col-' let as the point of bearing is still somewhat in rear ofthis end.

With my improved construction the gripping bearing of the collet on thestock is normally at the center of the bowed bars, but when the rear endof. the stock bar passes beyond this point it will be gripped by theforward end of the collet, which will advance it to a point immediatelyadjacent to the chuck of the automatic machine.

By such a constrution a saving is effected which in the aggregateamounts to considerable value.

As specifically shown, A are the jaws of the chuck or collet for theautomatic machine which are operated in the usual manner by a lorigitu-.5 dinally movable sleeve B extending through the tubular revolvingspindle C which latter has a conical head D at its forward end forradially contracting said jaws. E is the feed collet which islongitudinally reciprocated within the sleeve B 1-0 by an inner sleeveF. As the mechanism for actuating the sleeves B and F forms no part ofthe present invention, it is not necessary to further describe the same.7

My improved feed collet E is formed of a tube 15- Which at its rear endhas a threaded portion G for engagement with the sleeve F, this portionbeing of an internal diameter in excess of the diameter of the stock barto be fed. At the forward end H the internal diameter is smaller 20 soas to be slightly less than the diameter of the stock bar, and to permitof the passage of said bar one side of this portion is slitted at I.Intermediate the portions G and H the tube is longitudinally slotted toform a series of bars J that are bowed inward so that the normal pointof bearing against the stock bar is substantially at the center of thelength of the collet and some distance in rear of the forward endthereof. The radial thickness of the bar J is less than that of theportion H and their forward ends are provided with fillets merging intothis portion so as to avoid a localization of stresses at such point.The collet is preferably formed of steel suitably heat treated to impartthereto the desired hardness and resiliency. With the construction asjust described, the stock bar such as L is first manually advancedthrough the collet E to engage its forward end with the jaws A of thechuck. The reciprocation of the collet E will then move the samerearward during the machining operation on the portion held by the jawsA and upon the cutting off of the finished work and release of the jawsthe stock will be advanced by the forward movement of the collet E.During this operation the point of gripping will be located at thecenter of the bars J and this continues until the rear end of the stockbar is advanced beyond such center. When this occurs the point ofgripping bearing will be transferred to the portion H which being ofsuch greater thickness will be tensioned by a very slight expansion dueto the larger diameter of the stock. This will permit the feeding tocontinue until the rear end of the stock bar reaches the front end ofthe portion H which is immediately adjacent the jaws A. Thus no portionof the bar is wasted excepting that which is engaged by the jaws A andis in rear of the finished work.

In the modified construction shown in Fig. 6 the outer surface H of theportion H is eccentric to the inner surface thereof to vary thethickness of the wall, with the slot I passing through the thinnestportion. This will permit a more uniform radial expansion of the innerdiameter of this portion and also a better gripping of the rear endportion of the stock bar.

What I claim as my invention is:

1. A feed collet comprising a tubular member of an internal diametergreater than the external diameter of the stock bar to be fedtherethrough, the extreme forward end of said tubular member having aradially inwardly extending portion of a diameter slightly less than theexternal diameter of the stock bar, the intermediate portion of saidtube being longitudinally slotted to divide the same into spaced barswith one of the slots extending through the forward end and said spacedbars being bowed inwardly to resiliently grip the stock whereby thestock bar when engaged with said bowed portions will expand the slottedforward end portion free from gripping engagement with said stock bar,and whereby said forward end portion will grip the stock bar when therear end of the latter passes out of engagement with said bowed portionsto continue the feeding to the extreme rear end of said stock bar.

2. A feed collet comprising a tubular member having an internal diametergreater than the external diameter of the stock bar to be fedtherethrough, the extreme forward end of said tubular member having aradially inwardly extending portion of an internal diameter slightlyless than the external diameter of said stock bar, said inwardlyextending portion having a rounded fillet between the same and theportion of larger internal diameter, the intermediate portion of saidtubular member being longitudinally slotted to divide the same intospaced bars, one of the slots extending through said forward end andsaid spaced bars being bowed inward to form a gripping bearing forengaging the stock bar, said tubular member being formed of resilientmaterial whereby the engagement of the stock bar with said bowedportions will expand said forward end portion to free the same from thestock bar and whereby said forward end portion will grip and continue tofeed said stock bar when the rear end thereof disengages from said bowedportion.

3. A feed collet comprising a tubular member of internal diametergreater than the external diameter of the stock bar to be fedtherethrough, the forward end portion of said tubular member extendingradially inward so that the internal diameter thereof is slightly lessthan the external diameter of the stock bar and the outer surface ofsaid end portion being eccentric to the inner surface thereof to form aprogressively changing radial thickness, the central portion of saidtubular member being longitudinally slotted to divide the same intospaced bars, one of the slots extending through the end portion on thethin side thereof and said bars being bowed inward for grippingengagement with the stock bar whereby the engagement of said stock barwith said inwardly bowed portions will expand the outer end to free thestock bar and whereby said outer end portion with its varying thicknessof wall will resiliently clamp the stock bar when the rear end thereofpasses out of engagement with said bowed portion.

SAMUEL BAXENDALE,

